The present invention relates to remote terminals for use in digital loop carrier transmission systems, more specifically to terminals configured for providing broadband services such as video and high speed data to subscribers in the digital loop carrier serving area.
Public switched telephone networks have served subscribers by transporting telephone signals between a central office and customer premises equipment using a subscriber loop, also referred to as the local loop. The local loop is composed of wires, poles, terminals, conduits, and other outside plant that connect customer premises equipment to the central office of the local exchange carrier. The distance that a copper subscriber loop can be extended from a given central office can be many thousands of feet.
Loop carrier systems have been developed to improve the economics of loop deployment for services such as POTS and ISDN in a given central office. In subscriber loop carrier (SLC) systems, such as digital loop carrier (DLC) systems, bidirectional communication usually occurs between a central office (e.g., a local digital switch), a central office terminal (COT) and a remote terminal (RT), located in the vicinity of a customer""s premises. Information is transferred between the central office and the COT according to Bellcore TR-008, TR-57, and TR-303 interface standards. Information between the COT and RT is carried as 64 kb/s encoded digital channels multiplexed on an optical transport, for example an OC-3 SONET transport. The remote terminal includes optical to electrical interfaces for converting the OC-3 signal from the incoming optical fiber into an electrical signal, and a demultiplexer for demultiplexing the 64 kb/s digital telephone channels, which are directed to telephone line cards. Each telephone line card is usually configured to serve several customers, according to either POTS or ISDN protocol via respective copper pairs supplying two-way telephone signals to respective subscriber premises equipment.
Proposals have been suggested for utilizing the digital loop carrier infrastructure to provide transmission of broadband data, for example high speed data, multimedia or video services. One proposal suggests reserving a portion of the OC-3 transport capacity of the optical fibers between the COT and the remote terminal for broadband data, where a second broadband facility is output from the remote terminal to an adjacent remote terminal. Alternatively, a fiber may be run from the central office to the second remote terminal direct from the central office. In either case, the second terminal has asymmetrical digital subscriber line (ADSL) modem or other broadband line cards. The broadband data is passed via the second broadband facility, e.g. from the first remote terminal (having telephone line cards), to the second remote terminal (having broadband line cards) to modulate the broadband data onto the subscriber loops.
Such an arrangement, however, suffers from the disadvantage that an additional remote terminal must be installed adjacent to the existing remote terminal providing telephone service. This arrangement involves substantially increased costs associated with the expense of an additional remote terminal, plus legal issues involving the necessity of additional right-of-way for the additional remote terminals. Moreover, the ADSL modem cards cannot be connected to the corresponding subscriber loops without providing a tap between each of the twisted wire pair connections between the first remote terminal and the second remote terminal. This further increases costs due to manual rewiring and decreased stability due to substantially complex twisted pair connections.
U.S. Pat. Nos. 5,534,912 to Kostreski and 5,608,447 to Farry et al., the disclosures of which are incorporated in their entirety by reference, illustrate video networks that use ADSL modems for supplying broadband video data to a subscriber. For example, FIG. 4 of U.S. Pat. No. 5,534,912 to Kostreski discloses ADSL xe2x80x9cmuldemsxe2x80x9d that modulate video signals onto different frequencies and a frequency combiner 320 that outputs the modulated video signals as a combined spectrum to an intermediate distribution point 330 via a fiber plant. The intermediate distribution point 330 includes a plurality of ADSL filter/combiners 355. Each ADSL filter/combiner unit 355 receives a copper twisted wire pair for a selected subscriber from the standard telephone facilities 365, frequency multiplexes the telephone signals with the ADSL-modulated signals, and supplies the frequency multiplexed signals to the subscriber premises 360 via a copper twisted wire pair. The remote ADSL unit 305xe2x80x2 at the subscriber location 360 receives and demultiplexes the various telephone, video, and embedded operations channel (EOC) and control signals for use as required.
U.S. Pat. No. 5,608,447 to Farry et al. discloses in FIG. 11 an intelligent access peripheral (IAP) having an ADSL unit that frequency multiplexes broadband data onto subscriber loops. In particular, the IAP has a first port that receives broadcast video in ATM cell format from a broadcast headend, a second port that receives a second ATM cell stream carrying non-broadcast (point-to-point) data, and a third port that receives a copper pair (POTS) connection from a POTS switch. The IAP extracts the ATM cell streams from the first and second ports, and outputs digital video information and the telephone signals (POTS or ISDN) to the subscriber premises.
As is apparent from the foregoing, both U.S. Pat. Nos. 5,534,912 to Kostreski and 5,608,447 to Farry et al. require a separate distribution component (e.g., intermediate distribution point 330 or IAP) that requires a twisted pair connection from a POTS switch in order to multiplex digital video data with the corresponding telephone signals for transmission as a combined spectrum signal to a subscriber. As described above, these broadband distribution points, if implemented in a digital loop carrier serving area, would still require installation of the broadband distribution unit in addition to the existing remote terminal. Moreover, the broadband distribution units would still require a tap between each of the twisted wire pair connections from the remote terminal to the broadband distribution units in order to provide telephone service. Hence, the Kostreski and Farry et al. patents still suffer from the disadvantage of requiring a second distribution unit in addition to an existing remote terminal, plus the necessity of a tap between each of the twisted pair connections between the original remote terminal and the broadband distribution units.
There is a need for an arrangement for adding broadband services in an existing digital loop carrier system having a remote terminal configured for transporting information between a central office and the subscriber premises by respective subscriber loops, in a manner that avoids installation of additional remote terminals within the digital loop carrier system.
There is also a need for an arrangement that enables transport of broadband data in a digital loop carrier system, without requiring labor-intensive taps to be installed between POTS line interface cards and separate xDSL equipment.
There is also a need for providing broadband data services to subscribers in a digital loop carrier serving area, without the necessity of installing a separate distribution infrastructure to the subscriber premises equipment for the broadband data services.
These and other needs are attained by the present invention, where a remote terminal configured for providing communication between a central office and subscriber premises equipment within a digital loop carrier serving area includes integrated subscriber line circuits. The integrated subscriber line circuits are configured for providing either a downstream broadband data connection or both telephone-based connections and a downstream broadband data connection for each subscriber loop served by the integrated subscriber line circuits.
According to one aspect of the present invention, a remote terminal provides communication between a central office and subscriber premises equipment within a prescribed serving area. The remote terminal comprises a first bus for carrying digitally multiplexed narrowband data channels to and from the central office, a second bus for carrying digitally multiplexed broadband data channels, and a set of first subscriber line circuits, connected to the first bus, for logically connecting first subscriber loops serving a first group of subscribers to the narrowband data channels. The remote terminal also includes a set of second subscriber line circuits, connected to the first bus and the second bus, for logically connecting second subscriber loops serving a second group of subscribers to the narrowband data channels and the broadband channels, and a terminal controller for controlling logical connections between the first subscriber loops and the narrowband data channels, and between the second subscriber loops and the narrowband data channels and the broadband channels. The first subscriber line circuits provide conventional telephone service to the first group of subscribers, while the second subscriber line circuits provide enhanced telephone and broadband services to second subscriber loops by logically connecting the second subscriber loops to the narrowband data channels of the central office and the digitally multiplexed broadband channels. The broadband channels provide broadband data, for example from a broadband source such as a broadband information provider. Hence, the remote terminal can be used to provide both conventional telephone service, plus telephone and broadband services by integrating a broadband connection from a broadband data source with the narrowband data channels used for telephone communications between the central office and the subscribers in the prescribed serving area. The remote terminal may also be used to serve broadband-only subscribers without the need for a second remote terminal.
Another aspect of the present invention provides a remote terminal for providing communication between a central office and subscriber premises equipment within a digital loop carrier serving area. The remote terminal comprises digital subscriber line circuits, each receiving digitally multiplexed narrowband data channels from the central office and digitally multiplexed broadband data channels from a broadband data source, and each configured for selectively establishing a two-way narrowband data connection between the central office and at least one corresponding subscriber loop on a corresponding selected one of the digitally multiplexed narrowband data channels, and a two-way communication interface between the at least one corresponding subscriber loop and a broadband data source on one of the digitally multiplexed broadband data channels. The remote terminal also includes a controller for logically controlling establishment of the two-way narrowband data connections and the two-way communication interfaces by the digital subscriber line circuits. The digital subscriber line circuits each provide a two-way narrowband data connection, for example for telephone service, and a two-way communication interface for interactive broadband communications between the subscribers in the digital loop carrier serving area and a broadband information provider. Hence, broadband services can be provided to subscribers in a digital loop carrier serving area, without the necessity of building additional distribution infrastructure for broadband services. Moreover, the remote terminal enables ubiquitous service to be provided in a given central office area, where subscribers served by copper from a central office and remote terminal subscribers can both obtain service upgrades by changing the office equipment for the corresponding twisted pair. Hence, subscribers can obtain the same service, regardless of whether the subscribers have copper-based service (i.e., twisted wire pair connections to central office equipment) or carrier-based service with a remote terminal.
Still another aspect of the present invention provides a multichannel information distribution system for supplying communication between a central office and subscribers in a digital loop carrier serving area, the system comprising a first set of optical fibers carrying digitally multiplexed voice channels from the central office, a second set of optical fibers carrying digitally multiplexed broadband data channels from a broadband source, and a remote terminal connected to the first and second sets of optical fibers. The remote terminal includes digital subscriber line circuits, each digital subscriber line circuit establishing a two-way connection between at least one subscriber premises equipment and the central office, a downstream broadband connection between the broadband source and the corresponding at least one subscriber premises equipment, and an upstream data connection between the at least one subscriber premises equipment and an information provider supplying broadband data via the corresponding downstream broadband connection. The system also includes a plurality of subscriber loops, each carrying signals between the remote terminal and the corresponding subscriber premises equipment associated with the two-way connection, the downstream broadband connection, and the upstream data connection. Use of digital subscriber line circuits capable of establishing the two-way connection, the downstream broadband connection and the upstream data connection enable each subscriber premises equipment to concurrently receive both telephone and interactive broadband data services in a digital loop carrier serving area, without the necessity of installation of a separate broadband network distribution infrastructure. Moreover, a subscriber having only telephone service can easily be upgraded to receive broadband service by changing the corresponding line circuit from the first subscriber line circuit to the second subscriber line circuit. Hence, subscriber services can be upgraded merely by changing the appropriate line circuit serving the corresponding subscriber.
Still another aspect of the present invention provides a method of providing communication between a central office and central office subscribers in a digital loop carrier serving area. The method includes receiving, by a remote terminal serving the central office subscribers, digitally multiplexed voice channels from the central office via an optical fiber, receiving digitally multiplexed broadband data channels by the remote terminal, and selectively establishing in an integrated remote terminal line card, for each subscriber loop serving a corresponding subscriber premises equipment, at least one of a two-way communication interface between the corresponding subscriber premises equipment and the central office, a downstream broadband connection for supplying broadband data from one of the broadband data channels to the corresponding subscriber loop, and an upstream data connection for outputting data received from the corresponding subscriber loop to a service provider supplying the broadband data.
Yet another aspect of the present invention provides an integrated digital subscriber plug-in line card comprising a multiplexer/demultiplexer for logically connecting a plurality of two-way narrowband data paths serving respective subscriber loops to a bus configured for carrying digitally multiplexed narrowband data between the integrated digital subscriber plug-in line card and a central office, and telephone line interface units for connecting the two-way narrowband data paths by sending/receiving telephone signals for the respective subscriber loops. The integrated digital subscriber plug-in line card also includes a broadband data terminal adapter configured for receiving a digitally multiplexed broadband data stream and outputting a plurality of demultiplexed broadband data streams for the respective subscriber loops, the broadband data terminal multiplexing upstream control data streams, received from the respective subscriber loops, onto the digitally multiplexed data stream, a plurality of digital subscriber loop modems for modulating the demultiplexed broadband data streams into downstream analog signals, respectively, and demodulating upstream subscriber loop control signals received from the subscriber loops into the upstream control data streams, respectively, and a plurality of subscriber loop multiplexer/demultiplexer circuits for transmitting the downstream analog signals and the telephone signals to the respective subscriber loops at first and second signal channels, respectively, and demultiplexing the upstream subscriber loop control signals from the respective subscriber loops at a third signal channel. The broadband terminal adapter enables the integrated digital subscriber plug-in line card to send/receive data associated with broadband data services, independent of the bus serving the central office narrowband data. Hence, the integrated digital subscriber plug-in line card enables broadband data services to be provided to a plurality of subscribers without disruption or modification of the telephony infrastructure.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part may become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.